The present invention relates to a preparatory locating procedure and positioning of a device to be used in conjunction with a non-invasive comminution of concrements in the body of a living being, under utilization of shock waves for purposes of the comminution proper (extra corpo real shock wave lithotripsy), while ultra-sonics are to be used for the locating purposes.
German Pat. No. 23 512 47 (see also U.S. Pat. No. 3,942,531) discloses a device for the comminution of concrements in the body of a living being under utilization of a shock wave source. This source is placed in a first focal point of a focusing chamber being constructed as part of a rotationally symmetrical ellipsoid and being positioned so that the second focal points coincides with a concrement. The shock wave is usually produced by way of spark discharge. The practicing of comminution of kidney stones, without operative (invasive) procedure, and without the introduction of probes has been successfully practiced. An extensive description of equipment and therapeutic procedure is for example found in "Extracorporal shock wave lithotripsy", Ch. Chaussy ed., Munich 1982.
This kidney lithotripter was delivered in the beginning of 1984, by applicant's assignee and uses as a locating device two X-ray systems, in order to determine the exact position of the kidney stone, and in order to determine also its size. This locating procedure is also for example described in "The Dornier Kidney lithotripter" ZMV2 07-8403500. Once having located at least approximately the particular concrement such as a kidney stone the patient is shifted vis-a-vis the shock wave generating and focusing system for purposes of positioning, so that indeed the stone will coincide with the second focal point of the focusing chamber. Having located the particular stone and having placed the patient in the particular position necessary for a successful comminution process, the shock waves are triggered and the stone is in fact comminuted into a fine grit. Natural process of the body flushes the particles out of the system. The device for producing the shock wave field as well as the locating equipment are arranged so that they will not mutually interfere with each other as far as their individual function and purpose is concerned.
Typically, the two X-ray devices for locating the kidney stone are disposed next to the shock wave generator and reflector and on, so to speak, opposite sides or an axis of the generator. The two central beams of the two X-ray equipments intersect the axis of the reflector running through the two focal points, and under an angle of about 40 degrees each; the intersection of course should be situated near or right in the location of the kidney stone. Essential is a kind of orientation fixing which establishes a spatially fixed and thus structural unity between X-ray locating and patient/shockwave generating equipments; everything has to be moved vis-a-vis the patient. It is apparent that from an equipment point of view, the utilization of two full X-ray equipment and devices is relatively expensive. Moreover this utilization entails cutting into the reflector or portions thereof the windows which permit the passage of X-rays. And last but not least the patient receives, so to speak, a double dosage of X-rays.
Between the body and the reflectors along the shortest path into the body from the reflector, one usually provides a certain water coupling path in order to make sure that the shock wave propagating medium, namely water, does not substantially change in between the two focal points. On the other hand placing water in between the body and X-ray equipment deteriorates the performance of this locating equipment, so that care has to be taken that the X-rays will not pass through water. Alternatively certain steps have been taken in the past towards restricting the water path between the shock wave equipment and the body so as to avoid passage of X-rays through water.
As an alternative the locating and positioning, procedure as defined, ultrasonic is suitable and practical for a variety of reasons. As far as positioning the concrement is concerned, i.e. shifting either the body or the concrement itself in one form or another, ultrasonics is comparatively slow and, therefore, not as desirable or reliable as X-rays are, because the search process is difficult under utilization of a mechanical oscillator being fixed in relation to the shock wave lithotripter. It has to be considered that, so to speak, the human body has also ultrasonic entrance windows, which poses limitations in the application of ultrasonics for purposes of generating images representative of the interior or interior portions of the human body. The various organs and their movement are aspects which limit so to speak this window. Also, it is not only necessary to find the right spot on the surface of the human body through which ultrasonics and shock waves may enter but one needs the proper direction so as to bypass impediments of that window (keyhole effect).